Addition, conjugate, definition

Markovnikov orientation the 1,2-addition of an unsymmet-rical electrophilic reagent to an alkene with attachment of the more positive moiety of the reagent (H in the original definition) to the less substituted carbon Michael addition conjugate addition addition of a nucleophile to the /3-position of a carbon-carbon double or triple bond that is conjugated to a carbonyl or other electron-withdrawing group... 

Buffers are solutions that tend to resist changes in their pH as acid or base is added. Typically, a buffer system is composed of a weak acid and its conjugate base. A solution of a weak acid that has a pH nearly equal to its by definition contains an amount of the conjugate base nearly equivalent to the weak acid. Note that in this region, the titration curve is relatively flat (Figure 2.15). Addition of H then has little effect because it is absorbed by the following reaction ... 

The description of conjugated dienes as shown by equation 17 and the associated comparison with butadiene in equation 18 corresponds most closely to the conventional definition. The results are plausible in that groups on one double bond that are c/5-situated relative to the other encourage nonplanarity, cause destabilization and result in lessened conjugation energy. Or so we say. The biggest debit of this approach is that the thermochemistry of the monoenes related by single addition of H2 is often absent. An example... 

The term carbometallation was most probably coined only about a quarter of a century ago.1 However, the history of those reactions that can be classified as carbometallation reactions is much older. If one includes not only the Ziegler-Natta-type organometallic alkene polymerization reactions2 but also various types of organometallic conjugate addition reactions,3 carbometallation collectively is easily more than a century old. In its broadest definition, carbometallation may be defined as a process of addition of a carbon-metal bond to a carbon-carbon multiple bond. As such, it may represent either a starting material-product relationship irrespective of mechanistic details or an actual mechanistic microstep of carbon-metal bond addition to a carbon-carbon metal multiple bond irrespective of the structure of the product eventually formed. 

In addition, five heterodiphospholes (T-X) are known and are also dealt with in this chapter. Within the scope of this chapter are five-membered rings with three and four phosphorus atoms but no other heteroatoms. In these systems, full cyclic conjugation can only be attained if all phosphorus atoms are two-coordinate. The ring consequently must be negatively charged as in the 1,2,4- and 1,2,3-triphospholides (Y, Z) and in the tetraphospholides (iE). The pentaphospholide (0) is again beyond the definition but must not be excluded here. 

Structures 1 and 1, with identical relative configuration at C-2. C-3, are not covered by Masamune s very scant directions which do not include a guideline on the definition of the backbone. Thus, an allylmetal expert , having prepared 1 as one member of a series with the substituent of the ally] group varied, will probably describe 1 as syn, but investigators working on aldol reactions or conjugate additions will certainly prefer the term anti for 1. ... 

Definition and causes of jaundice Jaundice (icterus) refers to the yellow color of the skin, nail beds, and sclerae caused by deposition of bilirubin, secondary to increased bilirubin levels in the blood. There are three major forms of jaundice hemolytic jaundice, caused by massive lysis of red blood cells, releasing more heme than can be handled by the reticuloendothelial system obstructive jaundice, resulting from obstruction of the bile duct and hepatocellular jaundice, caused by damage to liver cells that decreases the liver s ability to take up and conjugate bilirubin. In addition, neonatal jaundice is caused by the low activity of hepatic glucuronylation of bilirubin, especially in premature infants. 

Reactions of this type are referred to in a variety of terms, many of which are rather confusing and nondescriptive. They sometimes are classified as 1,4-additions, implying that addition occurs across the terminal positions of the conjugated system. A synonymous term is conjugate addition. When the nucleophile is a carbanion, the reaction is called a Michael addition. Thus, by this definition, Equation 17-7 represents a Michael addition. Another, perhaps more typical, example is the addition of an enolate to a conjugated ketone ... 

Interesting and useful variations in R involve more complex alkyllithium reagents. For example, the treatment of (3-iodoenone (10) with lithium phenylthio(2-vinylcyclopropyl)cuprate gave the conjugate addition product (11) as an intermediate en route to the bicyclic dienone (12 82% equation 9).35 The ability of a cuprate to deliver a functionalized group to the enone was a definite advantage in this synthetic scheme. 

If there are other work terms, the reversible forms of which are Svv oth = L dl, where l is a displacement coordinate and L is the force conjugate to the displacement coordinate, we will include additional terms of the form —LI in the definition of the enthalpy. Although not all authors adopt this extended definition, it is necessary, as shown below, to maintain the form of Eq. (23). 

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